The purpose of this protocol is to evaluate neutrophil structure and function. The first approach utilizes micropipet manipulation techniques to study the relationship between chemokine concentration and neutrophil motility responses. The dependence of pseudopod extension on the concentration of fMLP and PAF is characterized. The second investigation utilizes the biointerface probe apparatus to study the compressive (as opposed to tensile) features of the neutrophil cell interface, especially the microvilli and the cortical network that exists under the plasma membrane and to which adhesion receptors are attached. Using the force probe as a nanoscale rheometer, the full course of cell surface contact, indentation, and surface recovery is tested as a function of loading rate.